1. Field of the Invention
The present invention relates to a heart rate monitor for measuring the heart rate of a subject person while doing exercise such as running, jogging and walking, while doing light exercise, or during medical treatment.
It should be noted that the heart rate in this invention means xe2x80x9coccurrences of pulse per unit timexe2x80x9d.
2. Description of the Related Art
As a method of measuring a heart rate, there are conventionally a method of detecting an electrocardiographic signal from electrodes attached to an area near a heart as disclosed in Japanese Patent Application Laid-open No. 60-116325, a method of optically detecting a pulse rate from a blood vessel of a lobe as disclosed in Japanese Patent Application Publication No. 61-43057, a method of detecting pressure pulsation by mechanical vibration from an artery near a body surface as disclosed in U.S. Pat. No. 4,038,976, and a method in combination with a hemodynamometer as disclosed in Japanese Patent Application Laid-open No. 4-279146.
However, the prior arts described above have the following problems to be solved.
Specifically, at first, in the method of detecting an electrocardiographic signal from electrodes attached to an area near a heart, it is necessary to fix the electrodes for detecting an electrocardiographic signal in contact with the skin of a thorax, and thus a band with a stretching properties, wound around the thorax is usually used. For this reason, a subject person has to be naked temporarily so that this band can be attached to him or her, and the chest is secured with such strength as to prevent this band from falling off, which sometimes gives a feeling of strain to the subject person if it is attached to him or her for a long period of time. Further, even if a heart rate is measured by the electrocardiographic signal collected at the thorax, in order to transmit it to the subject person, it is necessary to provide a display unit at a wrist or the like and send a signal to the wrist from the thorax by means such as radio.
Next, in the method of optically detecting a pulse rate from a blood vessel of a lobe, if a subject person does hard exercise such as running, there is the possibility of a measurement error occurring when the pulse rate is optically detected under the influence of body vibrations.
Even if the pulse rate is to be measured at a blood vessel where arteriovenous anastomosis exists as the blood vessel of a lobe, the aforementioned arteriovenous anastomosis has the function of adjusting bloodstream based on correlation between outside temperature and body heat, and therefore the bloodstream is decreased by this adjustment function to make the measurement difficult in some cases.
Further, in the method of detecting pressure pulsation by mechanical vibration from an artery near a body surface, body vibration has more influence than in the aforementioned method of optically detecting a pulse rate, and there is the possibility that a measurement error becomes large especially in the pulse rate detection during exercise.
In addition to it, in the method of performing detection in combination of a hemodynamometer, measurement can be made comparatively easily because a pulse rate is detected by an optical method or the like while a blood vessel is pressed with a cuff or the like. However, the burden that a measured region is pressed by the cuff or the like is imposed on the subject person during measurement.
In blood pressure measurement, the measurement is finished in a short time, and it is allowable that the measured region is pressed during that time. However, since heart rate measurement continues for a long time and measurement is needed during exercise, it is not preferable that the measured region is pressed by a cuff or the like.
The present invention is made in the aforementioned background, and is to provide a heart rate monitor, which imposes a very small burden on a subject person, is less susceptible to body vibrations accompanying exercise, and can measure the accurate occurrences of pulse per unit time, that is, a heart rate.
In order to solve the above-described disadvantage, trials and errors were repeated about taking out an accurate heart rate, with a burden on a subject person and a hindrance to exercise being made the smallest necessary limit, even under body vibrations of a subject person, and as a result, the present inventors have reached the following knowledge.
Specifically, in order to take out a heart rate with a burden on a subject person and a hindrance to exercise being made the smallest necessary limit even under the body vibrations of the subject person, it is preferable to reflect or transmit light at or through a blood vessel and/or blood, and thereafter detect the light.
Next, in order to collect an accurate heart rate, a thick artery in which arteriovenous anastomosis does not adjust bloodstream is preferable as a blood vessel at which the heart rate is taken out.
The present inventors have completed the invention of a heart rate monitor which can measure an accurate heart rate with a burden on a subject person and a hindrance to exercise being made the smallest necessary limit based on the above-described knowledge.
Specifically, a first aspect of the invention is a heart rate monitor comprising a light-emitting element, a light-receiving element, and a CPU, with
light from the aforesaid light-emitting element being reflected at or transmitted through blood running in a blood vessel,
the aforesaid light-receiving element detecting the reflected or transmitted light,
the aforesaid CPU measuring a change in bloodstream running in the vessel from a change in intensity of the light detected at the aforesaid light-receiving element, and
the aforesaid CPU calculating a pulse rate of the change in bloodstream per unit time from the measured value, and regarding the calculated pulse rate of the change in the bloodstream per unit time as a heart rate, and is characterized in that
the aforesaid light-emitting element and the aforesaid light-receiving element are fitted to a head of a human body having a space of 4 mm to 10 mm between them, and
light with a wavelength of 900 nm to 1200 nm emitted by the aforesaid light-emitting element is reflected at or transmitted through a subcutaneous artery and/or blood running in the subcutaneous artery and is detected at the aforesaid light-receiving element.
A second aspect of the invention is the heart rate monitor described above, which further comprises a display unit for displaying the calculated heart rate, and characterized in that
the aforesaid display unit transmits the calculated heart rate to a measuring person and/or a subject person by means of a display, a voice, radio, and/or bone conduction.
A third aspect of the invention is the heart rate monitor which further comprises a storage device for storing the calculated heart rate.
A fourth aspect of the invention is the heart rate monitor which further comprises a head band fitted to a head of a human body, and characterized in that
the aforesaid light-emitting element, the aforesaid light-receiving element, the aforesaid CPU, and the aforesaid display unit are attached to the aforesaid head band.
A fifth aspect of the invention is the heart rate monitor which further comprises an eyeglass frame fitted to a head of a human body, and characterized in that
the aforesaid light-emitting element, the aforesaid light-receiving element, the aforesaid CPU and the aforesaid display unit are attached to the aforesaid eyeglass frame.
A sixth aspect of the invention is the heart rate monitor which further comprises a sun visor fitted to a head of a human body, and characterized in that
the aforesaid light-emitting element, the aforesaid light receiving element, the aforesaid CPU and the aforesaid display unit are attached to the aforesaid sun visor.
A seventh aspect of the invention is the heart rate monitor which further comprises a container engaged in an ear pinna of a human body, and characterized in that
the aforesaid light-emitting element, the aforesaid light-receiving element, the aforesaid CPU and the aforesaid display unit are attached to the aforesaid container.
An eighth aspect of the invention is a method of measuring a heart rate comprising the steps of
fitting a light-emitting element and a light-receiving element to a human body,
reflecting or transmitting light emitted by the aforesaid light-emitting element at or through blood running in a blood vessel and detecting it at the aforesaid light-receiving element,
measuring a change in bloodstream running in the blood vessel from a change in intensity of the light detected at the aforesaid light-receiving element, and
calculating a pulse rate of the change in bloodstream per unit time from the calculated value and regarding the calculated pulse rate of the change in blood stream per unit time as a heart rate, and is characterized in that
the aforesaid light-emitting element and the aforesaid light-receiving element are fitted to a head of a human body with a space of 4 mm to 10 mm between them, and
light with a wavelength of 900 nm to 1200 nm emitted by the aforesaid light-emitting element is reflected at or transmitted through a subcutaneous artery and/or blood running in the subcutaneous artery and is detected at the aforesaid light receiving element.